Function SumColor(rColor As Range, rSumRange As Range)
''''''''''''''''''''''''''''''''''''''
'Written by Ozgrid Business Applications
'www.ozgrid.com
'Sums cells based on a specified fill color.
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Dim rCell As Range
Dim iCol As Integer
Dim vResult

iCol = rColor.Interior.ColorIndex
For Each rCell In rSumRange
If rCell.Interior.ColorIndex = iCol Then
vResult = WorksheetFunction.Sum(rCell) + vResult
End If
Next rCell
SumColor = vResult
End Function


via 2 Excel Functions/Formulas to Count/Sum Excel Cells by Color – Excel VBA User Defined Functions.

ColorIndex Property
The ColorIndex property can generate up to 57 colors. The table shown in Figure 1 illustrates the range of colors. The table was created programmatically by using a procedure similar to one shown later in the linked article. Figure 1. ColorIndex values and colorsFigure 1 shows the color palette and the corresponding integer value assigned to the ColorIndex property to produce the color. The ColorIndex property can be applied to the following parent objects:Interior ObjectFont ObjectBorder ObjectBorders ObjectFormatColor ObjectTab Object

via Adding Color to Excel 2007 Worksheets by Using the ColorIndex Property.

There are two types of reference styles in Excel. The first one is A1 reference style where the columns are labeled using the Alphabets and the rows are labeled using numbers. In the R1C1 reference style both the rows and columns are labeled using numbers.
Earlier versions of Excel from MS Office came with only R1C1 reference style. But recent versions like Office 2007 has both referencing styles. For example, in A1 Reference Style, E15 refers to the cell in 15th row and Eth 5th column and the same cell in R1C1 Reference Style uses R15C5 R followed by the row number and C followed by the column number. Most people prefer to use A1 reference style as both the labels for rows and columns are different. But with the R1C1 reference style since both rows and columns are numbered its easy to get confused especially while writing formulas. Also these reference styles are not only different in addressing but also very different in the way they are referenced in formulas or when selecting a range of cells.
In A1 reference style, the range is referred by the starting cell address and ending cell address with a colon in between. Example, A1:A5. This refers to the first five cells in the first column and this reference remains the same where ever the range is called within the sheet. But in R1C1 reference style the range is referred by how far the cells are located from the cell you are calling. For example, if you have 5 values from R1C1 to R5C1 and the range is called from R7C2, then the range would be R[-6]C[-1]:R[-2]C[-1]. Here the first cell in the range is 6 rows before the cell R7C2 and 1 column before the cell R7C2 and similarly for the last cell in the range. This method of referencing is called Relative Referencing. 
Though relative referencing is used by default in R1C1 reference mode, one can also use absolute reference with R1C1. For the same example as above, with absolute reference, the range would be referred as R1C1:R5C1. If you are writing a macro but you don’t want to get confused then you may switch to A1 reference style and write all the formulas and then switch back to R1C1 reference style to get the value of the formulas in this reference style.
Read more on: How to switch between A1 and R1C1 Reference Style in Excel?

via A1 and R1C1 Reference Style in Excel.